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  1. Couchbase Server
  2. MB-42092

Remove hash detail stats from cbcollect

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    • Story Points:
      1

      Description

      During qualification testing of 6.6.0 it was noted that memcached stats hash detail has a sizeable impact on server performance (ops/s).

      The exact cause of that slowdown has not been confirmed, but the belief is that given "hash" must traverse every item in each vBucket's HashTable and (while under lock) accumulate various stats including histograms of chain depth :-

      class HashTableDepthStatVisitor : public HashTableDepthVisitor {
      public:
          void visit(int bucket, int depth, size_t mem) {
              (void)bucket;
              // -1 is a special case for min.  If there's a value other than
              // -1, we prefer that.
              min = std::min(min == -1 ? depth : min, depth);
              max = std::max(max, depth);
              depthHisto.add(depth);
              size += depth;
              memUsed += mem;
          }
      

      While this is being investigated and improved, temporarily remove this stat call from cbcollect to avoid impacting normal operation in customer environments.

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          Activity

          james.harrison James Harrison created issue -
          james.harrison James Harrison made changes -
          Field Original Value New Value
          Link This issue relates to CBSE-9027 [ CBSE-9027 ]
          james.harrison James Harrison made changes -
          Component/s ns_server [ 10019 ]
          Component/s couchbase-bucket [ 10173 ]
          Assignee Daniel Owen [ owend ]
          james.harrison James Harrison made changes -
          Assignee Daniel Owen [ owend ] James Harrison [ james.harrison ]
          owend Daniel Owen made changes -
          Fix Version/s 6.6.1 [ 17002 ]
          owend Daniel Owen made changes -
          Link This issue blocks MB-41023 [ MB-41023 ]
          owend Daniel Owen made changes -
          Link This issue blocks MB-40528 [ MB-40528 ]
          owend Daniel Owen made changes -
          Labels approved-for-6.6.1
          james.harrison James Harrison made changes -
          Resolution Done [ 6 ]
          Status Open [ 1 ] Resolved [ 5 ]
          owend Daniel Owen made changes -
          Status Resolved [ 5 ] Closed [ 6 ]
          owend Daniel Owen made changes -
          Resolution Done [ 6 ]
          Status Closed [ 6 ] Reopened [ 4 ]
          owend Daniel Owen made changes -
          Resolution Done [ 6 ]
          Status Reopened [ 4 ] Resolved [ 5 ]
          owend Daniel Owen made changes -
          Assignee James Harrison [ james.harrison ] Daniel Owen [ owend ]
          Status Resolved [ 5 ] Closed [ 6 ]
          drigby Dave Rigby made changes -
          Description {{memcached stats hash detail}} has a sizeable impact on server performance (ops/s). While this is being investigated and improved, temporarily remove this stat call from cbcollect to avoid impacting normal operation in customer environments. During qualification testing of 6.6.0 it was noted that {{memcached stats hash detail}} has a sizeable impact on server performance (ops/s). The exact cause of that slowdown has not bee

          While this is being investigated and improved, temporarily remove this stat call from cbcollect to avoid impacting normal operation in customer environments.
          drigby Dave Rigby made changes -
          Description During qualification testing of 6.6.0 it was noted that {{memcached stats hash detail}} has a sizeable impact on server performance (ops/s). The exact cause of that slowdown has not bee

          While this is being investigated and improved, temporarily remove this stat call from cbcollect to avoid impacting normal operation in customer environments.
          During qualification testing of 6.6.0 it was noted that {{memcached stats hash detail}} has a sizeable impact on server performance (ops/s).

          The exact cause of that slowdown has not been confirmed, but the belief is that given "hash" must traverse every item in each vBucket's HashTable and (while under lock) accumulate various stats including histograms of chain depth :-

          {code:c++}
          class HashTableDepthStatVisitor : public HashTableDepthVisitor {
          public:
              void visit(int bucket, int depth, size_t mem) {
                  (void)bucket;
                  // -1 is a special case for min. If there's a value other than
                  // -1, we prefer that.
                  min = std::min(min == -1 ? depth : min, depth);
                  max = std::max(max, depth);
                  depthHisto.add(depth);
                  size += depth;
                  memUsed += mem;
              }
          {code}

          While this is being investigated and improved, temporarily remove this stat call from cbcollect to avoid impacting normal operation in customer environments.

            People

            Assignee:
            owend Daniel Owen
            Reporter:
            james.harrison James Harrison
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            Watchers:
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              Dates

              Created:
              Updated:
              Resolved:

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